Band Gaps in Jagged and Straight Graphene Nanoribbons Tunable by an External Electric Field

TL;DR

This study investigates how external electric fields can tune the band gaps of jagged and straight graphene nanoribbons, revealing significant tunability up to 0.6 eV and potential for optoelectronic applications.

Contribution

It introduces a classification of jagged graphene nanoribbons and demonstrates their band gap tunability under in-plane electric fields using tight-binding calculations.

Findings

Band gaps can be tuned up to 0.6 eV with external fields.

Chevron patterns in jagged ribbons enhance band gap controllability.

Linear and quadratic dependencies of band gap on electric field are identified.

Abstract

Band gap control by an external field is useful in various optical, infrared and THz applications. However, widely tunable band gaps are still not practical due to variety of reasons. Using the orthogonal tight-binding method for $\pi$-electrons, we have investigated the effect of the external electric field on a subclass of monolayer chevron-type graphene nanoribbons that can be referred to as jagged graphene nanoribbons. A classification of such ribbons was proposed and band gaps for applied fields up to the SiO$_2$ breakdown strength ($1$ V/nm) were calculated. According to the tight-binding model, band gap opening (or closing) takes place for some type of jagged graphene nanoribbons in the external electric field that lays in the plane of the structure and perpendicular to its longitudinal axis. Tunability of the band gap up to $0.6$ eV is attainable for narrow ribbons. In the case of jagged ribbons with armchair edges larger jags forming a chevron pattern of the ribbon enhance the controllability of the band gap. For jagged ribbons with zigzag and armchair edges regions of linear and quadratic dependence of the band gap on the external electric field can be found that are useful in devices with controllable modulation of the band gap.